A Leg Up for OSU’s College of Engineering

January 23, 2014

We’ve come a long way since 1982

Researchers at OSU’s College of Engineering may be taking more than baby steps toward finding out how humans walk. According to a study published last month in The Journal of Experimental Biology, the specific interaction between the ankle, knee, muscles, and tendons is outlined. This knowledge leads to understanding a leg moving forward in a way that maximizes motion while using minimal amounts of energy.

Jonathan Hurst, an OSU professor of mechanical engineering and expert in legged locomotion in robots, says, “Walking is almost like passive falling. The robots existing today don’t walk at all like humans—they lack that efficiency of motion and agility.” The high-power “push off” when the leg leaves the ground has been observed for some time, but understanding how it actually worked was a tough nut to crack. That said, researchers now believe they have the information to move forward.

The study concluded this motion has two phases: alleviation and launching. In the alleviation phase the trailing leg surrenders the burden of supporting the body mass. Then in the launching phase the knee buckles, allowing the rapid release of stored elastic energy in the ankle tendons, similar to a catapult.

Daniel Renjewski, a postdoctoral research associate in the Dynamic Robotics Laboratory at OSU, says, “Contrary to what some other research has suggested, the catapult energy from the ankle is just being used to swing the leg, not add large amounts of energy to the forward motion.” Walking robots do not function this way, many use force to “swing” the leg forward from a make-shift hip point. Although this allows the robots to move, it is neither energy efficient or agile.

Hurst believes the new research will bring them closer to developing walking robots that can move with as little energy as animals use. This technology will undoubtedly be adapted to advanced prosthetic limbs, which could improve the lives of countless amputees.